In recent years, a demand for systems using a high frequency such as a millimeter wave radar and a broadband wireless LAN has increased. In order to provide these systems inexpensively, besides a reduction in price of a semiconductor itself, it is essential to reduce a cost necessary for inspection. The above inspection is to measure whether an IC satisfies its specification by actually inputting a high frequency signal, and all products to be shipped or a considerable number of products to be shipped are needed to be evaluated. In the evaluation, a high frequency measuring device and evaluation device are needed. Thus, money and time are necessary and it costs high for the evaluation. A system capable of evaluating products simply has been requested in order to reduce the cost for the above evaluation.
Further, there has been known a portable wireless terminal including: at least two antennas; a transmission/reception circuit to be used for transmitting and receiving signals; a reception circuit to be used only for receiving a signal; a signal strength detection unit detecting received signal strength of each of the above-described respective antennas; an antenna switching unit for connecting one of the above-described respective antennas to the above-described transmission/reception circuit and connecting the other of the antennas to the above-described reception circuit; and a control unit, based on received signal strength detected in the above-described signal strength detection unit, determining the antenna with the highest received signal strength of the above-described respective antennas and controlling the above-described antenna switching unit to connect the above-described antenna with the highest received signal strength to the above-described transmission/reception circuit.
Further, there has been known a variable attenuator being a variable attenuator attenuating a signal input to an input terminal to output the attenuated signal from an output terminal, the variable attenuator including: a plurality of transmission lines connected in series between the input terminal and the output terminal; a first resistance element connected in parallel to the transmission line connected to the input terminal; and a second resistance element connected in parallel to the transmission line connected to the output terminal.
Further, there has been known a high frequency switch device including first to third terminals, a first FET, a first inductor and a first capacitor connected in parallel to the first FET respectively, a first circuit having one end thereof connected to the first terminal, a second FET, a second inductor and a second capacitor connected in parallel to the second FET respectively, and a second circuit having one end thereof connected to the other end of the first circuit and having the other end thereof connected to the second terminal.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2004-363862    [Patent Document 2] International Publication Pamphlet No. WO 2006/100726    [Patent Document 3] Japanese Laid-open Patent Publication No. 11-46101